This proposed Merit Extension will continue a line of research initiated In 1983 that has evolved into an internationally recognized program, the Baltimore Hip Studies (BHS), dedicated to identifying, developing, and evaluating strategies to optimize recovery following hip fracture. This Merit Extension, which has two components, will extend findings from prior Merit Award studies and other BHS projects demonstrating that hip fracture results In dramatic changes in muscle, fat mass and muscle strength, bone density and strength, bone turnover markers, serum levels of hormones and inflammatory markers, as well as walking ability and other aspects of function. The goals are to: 1) study some of the key mechanisms on the pathway to changes in community ambulation in response to a Multi-modal Exercise Intervention (MMEI) delivered to this frail and disabled group of older persons (Component I); and 2) test, in a preliminary manner through a pilot/feasibility study of a different sample of patients, the additional benefit of adding a protein supplement following MMEI sessions to determine if there are important changes in bone, muscle, inflammation, and function (Component II). The MMEI, being tested in a recently funded Phase III randomized clinical trial (1R01AG035009) of 300 patients In three centers, is a home-based program that addresses deficits in endurance, strength, balance and function through 40 supervised sessions. The primary outcome of that RCT is the ability to ambulate independently in the community. Component I of this Merit Extension will be conducted as an ancillary study to the Phase III RCT by adding mectianistic measurements to the patients recruited in the Baltimore, Maryland clinical site (Minimum number enrolled = 60; 30 per group). Component II wiil recruit 30 additional patients and provide a whey based protein and amino acid supplement immediately after completing each ofthe MMEI sessions to examine added mechanistic benefits and feasibility. Participants in both components will be assessed prior to randomization (within 2 months post hospitalization for hip fracture), and again 4 and 10 months later in order to examine the immediate effects (primary outcome) and the sustained benefits of interventions. We also will work with an international group of experts to identify strategies to accelerate development and testing of interventions for this group of older persons who experience this sudden disabling event.